1. Field of the Invention
The present invention relates to a reflection characteristic measuring apparatus for a sheet specimen and, more particularly, to a reflection characteristic measuring apparatus which scans a sheet specimen on which a plurality of color samples for use in calibration of colors printed by printing devices are printed to continuously measure the reflection characteristics of the color samples arranged in a two-dimensional array. The present invention also relates to a method of calibrating the reflection characteristic measuring apparatus for a sheet specimen, and to a calibration reference plate for use in calibration of the reflection characteristic measuring apparatus for a sheet specimen.
2. Description of the Background Art
FIG. 13 is a schematic view showing an example of a sheet specimen 971 for use in calibration of colors printed by a printing device such as a color printer and the like.
FIG. 13 is a plan view of the sheet specimen 971. As shown in FIG. 13, the sheet specimen 971 has a specimen surface 972 on which a multiplicity of (typically, hundreds of) color samples 981 having different color tones and different densities are printed. The color samples 981 are typically rectangular or square in shape, and are arranged in a regular array both in the longitudinal direction and in the transverse direction of the sheet specimen 971. Such a sheet specimen 971 is also known as a “color patch chart” or the like.
For the calibration of a printing device, predetermined print data is initially inputted to the printing device to be calibrated to cause the printing device to print the color samples 981 shown in FIG. 13. Thereafter, the reflection characteristics of the printed color samples 981 are measured, and the colors printed by the printing device are calibrated based on differences between the measured values of the reflection characteristics and the reference values of the reflection characteristics which the color samples 981 should inherently have.
However, an attempt to measure the color samples 981 arranged in a two-dimensional array as shown in FIG. 13 by using a reflection characteristic measuring apparatus of a manual scan type as disclosed in National Publication of Translation No. 2003-521700 requires the manual scanning of the color samples 981 arranged in the two-dimensional array to result in complications.
To solve such a problem, a reflection characteristic measuring apparatus of an automatic scan type which automatically scans the color samples 981 arranged in a two-dimensional array has been put to practical use, as disclosed in Japanese Patent Application Laid-Open No. 2001-264173. The reflection characteristic measuring apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-264173 measures a distance between an illuminating and light-receiving system and a specimen surface of a sheet specimen to correct the measured values of the reflection characteristics of the color samples 981, based on the measured value of the distance. The reflection characteristic measuring apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-264173, however, presents a problem in that it takes a long period of time to scan the color samples. The reflection characteristic measuring apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-264173 presents another problem in necessitating a correction process to eliminate measurement errors resulting from variations in the distance between the illuminating and light-receiving system and the specimen surface of the sheet specimen.